Methods and systems for quantitative mass analysis

Abstract

A method of quantitative mass analysis of precursor species of different mass-to-charge (m/z) ratios from a single or the same ion injection event is disclosed. A plurality of precursor ion species having different respective m/z ratios are introduced into a mass spectrometer at the same time. The precursor ion species are isolated. A first subset of the isolated precursor ions having a first m/z ratio is fragmented and analyzed. A second subset of the isolated precursor ions having a second m/z ratio is fragmented and analyzed. A first mass spectrum is generated for the fragment ions of the first subset of precursor ions, and a second mass spectrum is generated for the fragment ions of the second subset of precursor ions.

What is claimed is: 
     
       1. A method of operating an ion trap mass analyzer for quantification of analytes in a sample, comprising:
 a. introducing sample ions into the ion trap mass analyzer in a single injection event, the sample ions including first precursor ions having a first mass-to-charge ratio (m/z) and second precursor ions having a second m/z; 
 b. concurrently isolating the first precursor ions and the second precursor ions; 
 c. fragmenting the first precursor ions, but not the second precursor ions, to generate first product ions; 
 d. performing a first scan to mass-selectively detect the first product ions and acquire a first mass spectrum including the first product ions, wherein an endpoint of the first scan is set such that the second precursor ions are retained in the ion trap mass analyzer; 
 e. fragmenting the second precursor ions to generate second product ions; and 
 f. performing a second scan to mass-selectively detect the second product ions and acquire a second mass spectrum including the second product ions. 
 
     
     
       2. The method of  claim 1  further comprising determining an amount of the analyte in the sample using a relationship between intensities of the product ions in the first mass spectrum and the second mass spectrum. 
     
     
       3. The method of  claim 1  wherein the first precursor ions are analyte precursor ions, and the second precursor ions are internal standard precursor ions. 
     
     
       4. The method of  claim 1  wherein the first precursor ions are internal standard ions, and the second precursor ions are analyte precursor ions. 
     
     
       5. The method of  claim 1  further comprising applying a notched waveform to concurrently isolate the first precursor ions and the second precursor ions from any background ions. 
     
     
       6. The method of  claim 1  wherein the fragmenting is carried out using ion trap collision-induced dissociation (CID). 
     
     
       7. The method of  claim 1  wherein an RF amplitude is scanned from a first point to an endpoint to eject the first product ions to the detector. 
     
     
       8. The method of  claim 1  wherein an RF amplitude is scanned from a first point to another endpoint to eject the second product ions to the detector. 
     
     
       9. An ion trap mass spectrometer system for quantification of analytes in a sample, comprising:
 a. an ion source configured so as to generate sample ions, the sample ions including first precursor ions having a first mass-to-charge ratio (m/z) and second precursor ions having a second m/z; 
 b. an ion trap mass analyzer positioned to receive the sample ions, the ion trap mass analyzer having a controller programmed to apply voltages to the ion trap mass analyzer to cause the ion trap mass analyzer to performs steps of: concurrently isolating the first precursor ions and the second precursor ions; and to fragment the first precursor ions, but not the second precursor ions, to generate first product ions. 
 
     
     
       10. The system of  claim 9  further comprising a notched waveform to concurrently isolate the first precursor ions and the second precursor ions from any background ions. 
     
     
       11. The system of  claim 9  wherein the fragmented first precursor ions and the fragmented second precursor ions are produced through collision-induced dissociation (CID). 
     
     
       12. The method of  claim 1  wherein the analytes in the sample are quantified using a single ion trap mass analyzer. 
     
     
       13. The system of  claim 9  wherein the ion trap mass analyzer is a single ion trap mass analyzer.